
Compton scattering of polarization entangled photons has been studied in the past by measuring a quantity known as the azimuthal ratio. This involves a coincidence measurement of both photons scattered through the same angle, i.e., \(\theta _{s}=\theta _{i}=\theta \)  [1]}, [2]}. The geometrical arrangement to measure the ratio of cross-polarized Bell states when the wave vectors are not colinear is illustrated schematically in Fig. (REF ). In this arrangement, the photon counter of the scattered idler is fixed at \(\phi _{i}=0^{o}\) , such that only idler photons scattered in the trajectory plane are detected. Using Eqn. (REF ), this implies \(\eta = \phi _{s}\) .
